Looking for callback function after Gutenberg is rendered?

On post/page editing screen, I want to call my functions as soon Gutenberg editor/whole page is fully rendered and visible. On WP 5.2.2, I have tried jQuery(document).ready(function () {}); and wp.domReady(function() {}); but both of these functions are called before components are rendered.

Are there any similar function or callbacks are available that we can use in this situation?

Edit:
Scenario is, I am working on a plugin that allows the user to password protect children of a password protected parent page. For this, on page editing screen, I need to show a checkbox just below the password field which will allow user to select whether child pages of this page should also be locked or not.

I had it working for WordPress versions earlier than 5.0, but since Gutenberg, it is broken. If there is a better way to do it, I would love to learn.

Thanks